>> Hello, and welcome to the Penguin Prof Channel.
In today's episode I want to talk about another one
of the four macro molecules of life.
I want to talk about lipids, and if you go to the grocery store,
and you go down what I call the "fat aisle", the aisle with all
of the oils and they're all advertising
to get your attention, and you should eat this one,
but not that one.
It can be unbelievably confusing,
so what is up with all of these lipids?
Lipids are actually really important molecules.
They pack a lot of energy or calories in to a small space.
They are all hydrophobic which means they do not mix with water
which you probably know, and we use them
for long term energy storage.
They also help to keep us warm, and we use them
to build membranes and organelles, a loss of hormones.
Lipids are really important for us.
The first group of lipids,
I just want to mention really briefly, are the phospholipids,
and these are the components of cell membranes, and they're made
of a backbone of glycerol, two fatty acid tails,
a phosphate group, and then a side chain.
I'm just basically mentioning them
because I have entire video on this.
If you watch "Meet the Cell Membrane" I talk
about the magic of phospholipids.
There's a link in the description box below.
Another group of lipids include the steroids,
and the most famous steroid, and the one from which we build all
of our steroid hormones is cholesterol.
Cholesterol, by the way, is only made by animals.
So, when you see those plant oil labels and they have
in huge letters, you know, this product is cholesterol free,
they didn't take the cholesterol out for you,
plants don't make cholesterol.
They are important for us though,
because we build our steroid hormones out of cholesterol,
and we can ask this question.
Actually, it's not really men versus women,
it's actually our steroid hormones.
Testosterone versus estradiol
which is the most common of the estrogens.
Who's really more stable?
Well, you may be surprised to see how similar testosterone is
on the left, to estradiol on the right, and if you think "wow,
those look almost identical" you're right.
There's only one real difference between the two.
Which one is more stable?
Well, if you know organic chemistry,
this is an alpha beta unsaturated carbonyl,
and the females, the estradiol, we have an aromatic ring.
And, if you know ochem you know the aromatic ring is a more
stable configuration.
So, at this level, at least, we win.
Estradiol is actually more stable.
Just thought I'd mention that.
We're going to spend the rest of the video talking
about this group of lipids called the glycerides,
and when we talk about the diet this is the group,
really that we're talking about.
This is a pretty typical one.
This is a triglyceride.
A triglyceride has a backbone of glycerol with three carbons,
and then here you see the fatty acid tails that are attached,
and when you talk about dietary fats generally you're talking
about triglycerides, so it's worth our while
to talk about them.
And, one of the most important things
about them has to do with this.
You see this on food labels all the time.
Saturated or unsaturated.
Which one is healthier?
And, what does it mean?
I mean if you ask people, saturated
or unsaturated with what?
Calories, or fat?
Or, cholesterol?
People have absolutely no idea, in general,
and unless you've studied biology or chemistry it's kind
of easy to see why, because it is a chemical answer.
It's actually saturated or unsaturated with hydrogens.
So, let's take a step back for just a second,
and we look at our Lewis Dot Structure for Carbon.
Now these penguins, if you recall,
represent the valance electrons for carbon.
Carbon has four electrons in its valance shell -
we'll actually go ahead and replace the penguins
with those dots right there, and I actually talked about this,
and explained all of this in my chemistry basic part one video,
and I put a link in the description below.
But, basically what this means is that carbon has
to have four bonds going to it in order to be stable.
In these fatty acid chains what you see is
that any given carbon is attached to one carbon that's -
we'll call it upstream, right?
Closer to the nepheline, one carbon downstream from it,
and then the other two spots are occupied by hydrogen.
So, remember every line represents one pair
of electrons being shared.
So, for the carbon in the center this is happiness.
It is perfectly stable here.
Now, if you have a fatty acid chain that looks like this,
you notice that every carbon
in the middle has two hydrogens attached to it
and we say it is saturated.
They can also be unsaturated, and what you're looking
for right there is that double bond.
Now, a double bond means
that those two carbons can't have two hydrogens attached,
because you can only have four covalent bonds.
So, you can only have now two hydrogens there.
Now, why this matters, if you're thinking, "Gosh, this is a lot
of detail" it turns out that this has real dietary
implications, because whether
or not there is a double bond impacts how this fatty
acid behaves.
Things like, is it solid or liquid at room temperature?
So, saturated fats, because they're very linear,
they tend to pack very tightly
and they'll be solid at room temperature.
Whereas, unsaturated fatty acids,
because the double bonds put a kink in the chain,
they tend to be liquid at room temperature,
because those fatty acid tails do not pack as tightly.
So, when you see that double bond,
that makes the chain a little kinky,
and that affects how it behaves.
So, in terms of the diet, saturated fats tend to come
from animal sources, things like butter, and cheese, and lard,
and meat, and meat products.
There are also some plant oils that are saturated.
These are the fats that you want to avoid or eat
in limited quantities, because they are the most difficult
for your cardiovascular system to manage,
and eating excessive amounts
of saturated fats can lead to heart disease.
Monounsaturated, mono just means one, so there's one double bond,
and you're going to get monounsaturated fats in lots
of different nuts, olives, pistachio's, as well as things
like avocados, and the oils from all of those guys.
Omega-6 polyunsaturated, now poly means many, you're going
to get those in sunflower seeds, and wheat germ,
and soybean oils, walnuts.
The omega-6's, as well as the omega-3 polyunsaturated,
these are the famous guys from lots of marine sources,
as well as walnuts, these tend to be very, very heart healthy.
So, you want to choose these polyunsaturated fats
when you are looking at fats in your diet.
So, as you go down, these are your best dietary sources,
and it turns out that these polyunsaturated fats
and the omega-3's in particular, are very heart healthy,
and have actually been shown
to reduce the risk of heart disease.
If you're wondering about the funky names here,
we name carbons in the chain from the methyl end
which we also call the omega end.
So, omega - 3 polyunsaturated fatty acids have their first
double bond at carbon number three,
whereas the omega-6 polyunsaturated fatty acids have
their first double bond at carbon number six.
So, there is a method to the madness.
Now this leads to the natural question,
what the heck is artificial hydrogenation,
which you're going to see on a lot of processed foods,
and you might be wondering what that's all about.
It actually means exactly what it sounds like.
You add hydrogens artificially.
Now, this is done by bubbling hydrogens
through extremely high heat vegetable oil.
We're talking about 250 to 400 degrees Fahrenheit,
vegetable oil, okay, in the presence of a metal catalyst
which is usually nickel, sometimes platinum, actually
and this process can take several hours.
And, what happens is these double bonds, these get broken
and you insert hydrogens in there.
Now, we call it partial hydrogenation
because full hydrogenation, or the creation
of all stearic fatty acid chains,
that turns out to be kind of gross,
and those fats are too waxy and actually too solid
for most food use purposes, so the process is actually stopped
at partial hydrogenation.
Okay, so what about trans fats?
We've got saturated fats which we've seen.
We've got unsaturated fats which we've seen.
These are trans fats.
Now, what's the difference?
An unsaturated fat has its two hydrogens on the same side
of the chain, and in chemistry we refer to that kind
of an isomer as sic, in Latin cis means on the same side.
Now the other way to do it, the trans isomer, trans is Latin
for across, and trans fats turn
out to be really nasty on the body.
You got to avoid them at all costs.
I could do a whole video on why you should avoid trans fats.
My friend who's a dietician says,
"you know it would be healthier to eat food covered
in rat droppings, than to eat trans fats" and its kind
of gross, but I think still a good visual.
The thing you have to understand is
that zero doesn't always mean zero.
You find trans fats in processed foods, especially snack foods,
and you may have trans fats even if it says "zero grams"
on the nutrition label.
The FDA allows that as long as the food has less
than half a gram of trans fat per serving.
That "per serving" turns out to be really important,
because if you eat more than one serving of chips, or cookies,
or microwave popcorn, you actually are getting trans fats,
and if you read the label you wouldn't know it.
So, that "per serving" turns out to be really important.
By the way, the FDA allows this for regular fats as well,
so you can say "fat-free" or "calorie free" as long
as the amount is very small,
but most people don't eat one serving of chips.
I mean, do you really eat only six chips?
So, how much fat really should we be eating,
because you do need some fat in your diet.
This is based on a 2000 calorie per day diet.
The healthy range is from 20 to 35 percent
of your calories from fat.
This is how many calories, and how many grams.
I did the math for you, and the American Heart Association
recommends no more than seven percent,
or 15 grams of saturated fat per day,
and the also recommend you avoid all trans fats.
So, I just got to show this.
If you eat a lot of fast food, here's a typical burger
and fries, and this is what you're actually getting,
68 grams of fat just from this all by itself.
Twenty-three grams of that is saturated,
and seven grams of trans fats.
So, I know you don't want to see it,
but I got to show it to you anyway.
This is where we're at.
The obesity epidemic is out of control.
We've got fast-food, we've got an abundance of fatty, salty,
sweet foods, and a sedentary lifestyle,
and this is what you get as a combination of all of that.
If you haven't seen this image, I think this is very powerful.
This is MRI scans of a 250-pound woman on the left
and a 120-pound woman on the right,
and you can see a number of things.
First of all, the collection of fat all over the body,
especially look at around the heart.
There should not be adipose capsule around the heart.
The heart on the left is also enlarged
to support this huge body mass, that is not good.
There's also an abundance of abdominal fat,
fat around all the organs, and look at the joints.
Oh my gosh, in the knees look at the ankles.
There's no cartilage left, everything is bowing
out from carrying this amazing amount of weight.
This is not good.
We must do something about this obesity problem.
We must start making healthier dietary choices,
and we got to get people off the couch and back
to a more active lifestyle.
That is the end of my soap box, as always.
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